One of the most violent but beautiful reminders that we live on ageologically restless planet are volcanic
2 }& `9 ~5 }5 q e0 Ctvb now,tvbnow,bttvberuptions. Around 550volcanoes have erupted at least once in historic times, and around 50or 60 are
& n9 m) z# {) m& N1 hTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。active each year. On any given day, as many as 10 volcanoesmay be spewing ash or lava somewhere on Earth.TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。* K$ _4 S, C2 k# B
Some volcanoes, such as Mount Etna in Italy, erupt almost constantlyfor years on end. Others, like Mount St. Helens,
6 v' F% k4 {7 J0 C M$ f0 o- K公仔箱論壇erupt rarely andsometimes extremely destructively. Like Etna and Mount St. Helens, manyof the most dangerous
. P7 c6 ]* B7 K# Q* t/ \1 xand explosive erupters are stratovolcanoes, whichare made of layers of ash and lava from previous eruptions. . q [6 x7 D/ T0 u
They tendto be steep-sided cone-shaped volcanoes and often rise strikingly abovethe surrounding landscape." o6 h* D1 @* b" `
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Many of the stunning images of eruptions captured from space are ofviolent stratovolcanoes, such as the one above
% A5 \) c1 X4 d8 i: w N公仔箱論壇of Kliuchevskoi, themost active volcano on Russia’s Kamchatka peninsula. The image abovewas
( C) L3 H) Q6 a* x* W- b% z" h* ~3 Dtaken by astronauts on the space shuttle Endeavour in 1994, as an eruption was just getting underway. The ash }6 P4 Y! W$ N7 L0 S
plume reached as high as 50,000 feet.
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Augustine Volcano is a 4,100-foot-tall, 7-mile-wide stratovolcano. This eruption was captured by NASA’s Terra
5 q) z( _1 Q q% Mtvb now,tvbnow,bttvbsatellite in 2006. Augustine’s dome collapsed in 1883, during its largest historical eruption. It has been erupting for at least 40,000 3 F" {$ K; N* d! k+ O
years. The island’s jagged edges were created by massive avalanches.
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Augustine lies in the Cook Inlet at the eastern end of the Aleutian trench which marks the northernmost portion of the Pacific Ring tvb now,tvbnow,bttvb; R/ t" h7 c- l" V% U+ C# B
of Fire. Volcanic activity here is caused by the subduction of the Pacific plate beneath the North American plate. As the wet tvb now,tvbnow,bttvb" O. c+ Q3 @' c) t! T5 {0 [, Y, T
ocean crust descends into the molten mantle below, superheated water is squeezed out and rises up to melt the bottom of 5.39.217.77' r+ a- T$ ?9 l; h( @( W: M- j0 ~1 k
the continental crust, creating magma that drives the volcanic eruptionsTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。. |6 r- M. V0 Y% d- \" D2 g
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Astronauts aboard the International Space Station caught a lucky glimpse of the start of this eruption of Sarychev Volcano
+ \/ G% k1 l/ g7 k8 H Gtvb now,tvbnow,bttvbin the Kuril Islands, northeast of Japan, on June 12, 2009. This was the volcano’s first eruption in 30 years.5.39.217.77: s5 F2 i5 ~ ?% V% k( h
2 S8 w, S% p. }$ u& q: H公仔箱論壇The smooth white cloud, known as a pileus cloud, topping the eruption column may be made of water condensation caused by rising 1 M* W9 U2 U+ ]9 u
and cooling of the air above. In contrast, a dark gray cloud of ash near the ground is probably an avalanche of hot ash and rock known
- @1 H( B0 b( a8 p) k3 eTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。as a pyroclastic flow.
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This photo sparked a debate among scientists about what caused the hole in the clouds above the eruption. Three possible options came up:公仔箱論壇+ \9 O) j" @9 X: p% c$ W+ ?! x3 a
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* It could have nothing to do with the eruption and simply be caused by the contrast in temperatures between the ocean and the island.
1 L$ @- \0 b9 Q% m1 v0 R$ htvb now,tvbnow,bttvb * A shockwave from the eruption could have blown a hole in the cloud deck.
, H3 W" W' g U) p* n) i/ CTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。 * As the plume rose, air flowed downward along the sides and became warmer and evaporated the clouds.
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5.39.217.77 _+ M3 C' F$ P+ z0 C
; V2 ]2 F3 {3 m# YTVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。Alaska’s Redoubt Volcano erupted five times in one night this year after almost three decades of relative quiet. tvb now,tvbnow,bttvb3 d! B4 l0 ]3 y. m5 U% `- C; _
It continued erupting on and off for weeks afterward. This image was taken by the commercial satellite GeoEye-1 on March 30 when
1 R U- z2 n2 ] ?5 ~tvb now,tvbnow,bttvb the ash reached heights of 27,000 feet. The volcano’s alert level is still “advisory,” and the aviation color code is yellow.
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Redoubt is a 10,200-foot tall stratovolcano 100 miles southwest of Anchorage in the Aleutian Range, west of the Cook Inlet.公仔箱論壇9 J" W+ ]# s1 W& r
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+ v$ O+ I7 v# e4 ~7 Htvb now,tvbnow,bttvbMount Etna is the second tallest volcano in Europe, at almost 11,000 feet. It is one of the most active volcanoes in5.39.217.77- V/ i4 U* O& r( {( p" J. {
the world and is erupting nearly continuously. It is no surprise that there are many great photos of this volcano erupting, including this one
: ^$ X8 |4 ]5 L( gtvb now,tvbnow,bttvbcaptured by astronauts on the International Space Station in 2002. The lighter colored plumes of smoke on the slope of the volcano in
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also be the oldest-known active volcano.
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* m# A+ d& B3 H p公仔箱論壇A NASA astronaut spotted this eruption of Cleveland Volcano from the International Space Station in 2006. The volcano is 5,700 feet high
* G% Q' y4 e1 J+ B2 W* M; Z8 w公仔箱論壇and claimed the only known eruption-related death in Alaska’s Aleutian Islands in 1944. Its symmetrical, cone shape is typical of stratovolcanoes.
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; I$ G& m1 @% X0 t# _公仔箱論壇Popoépetcatl, which means “smoking mountain” in the Aztec language, is a very active volcano just 44 miles outside Mexico City. tvb now,tvbnow,bttvb3 W+ g: g' ] m" f
The second highest peak in Mexico at 17,800 feet, this glacier-covered stratovolcano has erupted at least 20 times in the last 500 years and has caused 1 z; o |' W; G- A( Y
multiple evacuations of the city. This eruption in 2001 was caught by astronauts on the International Space Station, near the end of a seven-year period
" s6 e" R4 _: t1 P7 P% R$ l- Eof frequent activity. The plume reached heights of around 30,000 feet.5.39.217.77$ d% M+ l6 F: O& k
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This eruption of Chaitén caldera in Chile was photographed from the International Space Station in May 2008. Volcanism along the
9 i3 i& `% H: ^' {! {5.39.217.77west coast of South America is the result of subduction of the oceanic Nazca plate beneath the South American plate.5.39.217.774 m5 {# X5 {$ g' G, r- ]
4 t% }% W& k! a7 Z) k5.39.217.77Chaitén was last active more than 9,000 years ago. The violent 2008 eruption inundated the small coastal town of Chaitén with ash, pyroclastic
+ I" U8 I! j4 u [/ cflows and volcanic mudflows called lahars. The caldera is relatively small at less than two miles wide, and sits on the flank of the larger Michinmahuida volcano.TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。7 t/ E; k/ v3 H: d' u4 {- ~
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* k; ^! f/ F& S5 ^公仔箱論壇This image of the Sierra Negra volcano in the Galapagos Islands was taken by NASA’s Terra satellite in 2006. Sierra Negra 公仔箱論壇! m# ?, v. W3 e/ B* V
is a shield volcano, which are made mostly of previous lava flows and tend to be broad and gently sloping. The Galapagos are part of an island chain tvb now,tvbnow,bttvb' t1 t& f }; q$ d! ?/ {
formed by a hot spot where a plume of hot mantle rises up and melts the base of the ocean crust. As the Pacific plate moves over the relatively 5.39.217.77! h- [- L7 ]3 G$ L- \% z
stationary hot spot, volcanoes are formed. The Hawaiian Islands were formed — and continue forming — the same way.
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NASA’s Terra satellite snapped this image of Shiveluch volcano erupting on Russia’s Kamchatka peninsula at the edge of the Pacific Ring of Fire in 2004. TVBNOW 含有熱門話題,最新最快電視,軟體,遊戲,電影,動漫及日常生活及興趣交流等資訊。9 p. M- O1 a+ n6 ?& I
A lava dome had been growing in the volcano’s crater, followed by intermittent eruptions that lasted weeks. Shiveluch is a 10,400-foot-high stratovolcano
; X; z5 w. `* M- V7 A1 U公仔箱論壇that is at least 60,000 years old and has been erupting fairly often for the past 10 years. Its dome has collapsed multiple times, most recently in 1964, $ ?* l! r' ^( q9 O; V3 w1 r+ E+ O1 M
causing avalanches of debris into the crater. |